Optical switch and networking method

ABSTRACT

An optical node capable of automatically detecting its interconnectivity is disclosed. The node includes a light switch, a light source, light detector, a control circuit having a unique identification. The node sends its identification via each of its ports and also listens to each of its ports for identification from other nodes. The node may store the interconnectivity information, forward the interconnectivity information to another node, or forward the interconnectivity information to a path router.

BACKGROUND

[0001] The present invention relates to the art of data networks. Moreparticularly, the present invention relates to data networks usingoptical switches.

[0002] Because of ever increasing bandwidth requirements, data networksutilizing optical transmission systems are becoming popular. Opticaltransmission systems have a larger bandwidth compared to electricaltransmission systems.

[0003]FIG. 1 illustrates a simplified optical switching network 100including a plurality of input lines represented by lines 102 a, 102 b,and ellipsis 102 c (collectively, “102”) and a plurality of output linesrepresented by lines 104 a, 104 b, and ellipsis 104 c (collectively,“104”). In the network 100, three +optical nodes NA 110, NB 120, and NC130 are illustrated. Although only three nodes are shown, the switchingnetwork 100 may include hundreds or even thousands of interconnectedoptical nodes.

[0004] Node NA 110 has an optical switch 112, a control circuit 114, anda plurality of input lines and output lines, or ports, designated, forconvenience, NA0 to NAn where n is an integer. Typical values for n maybe 15, 63, or 255. The ports—NA0, NA1, . . . and NAn—are ports of thenode NA 110 as well as the ports of the switch 112. The switch 112 mayutilize micro mirrors, liquid, or gaseous elements (generically,“switching element”) to direct or reflect optical signals from a firstport to a second port. Typically, the ports are bi-directional but issometimes uni-directional. The control circuit 114, connected to theswitch 112, controls the state of the switching elements to implementNode NA 110 as described herein above is known in the art.

[0005] Nodes NB 120 and NC 130 are similarly configured to node NA 110,and their ports are similarly denoted herein. A path router 140 isconnected to nodes NA 110, NB 120, and NC 130. The path router 140contains physical path topology of the network 100 necessary to makeconnections as requested. The path router 140 contains the physicalnetwork topology of how the switches are connected.

[0006] For instance, in order for the path router 140 to successfullydirect an input signal at input line 102 b to an output line 104 b, thepath router 140 needs to know that (1) the input line 102 b feeds intoport NA7; (2) port NA9 is connected to port NB1; (3 port) NB8 isconnected to port NC7; and (4) port NC9 is connected to the output line104 b. With the information, the path router 140 signals node NA 110 toroute its port NA7 to its port NA9, signals node NB 120 to link its portNB1 to its port NB8, and signals node NC 130 to link its port NC7 to itsport NC9. The physical path topology information may be entered directlyinto the path router 140 or supplied by an external controller system(not shown), connected to the path router 140.

[0007] In the illustrated configuration, port NA9 is connected to portNB1 (connection 150) and port NB8 is connected to port NC7 (connection152). The other ports of nodes NA 110, NB 120, and NC 130 may beconnected to ports of nodes not show in FIG. 1. As the number of nodes,thus the ports, grows in the network 100, the number of possibleconnections grows exponentially. It is not uncommon to have a networkwith hundreds or even thousands of ports. Prior art requires that thephysical topology be configured manually.

[0008] Without a correct topology of the network 100 as defined by theconnection information of the routing table, the network 100 does notoperate effectively.

[0009] The processes of manually defining the full network physical pathtopology for the path router 140 are susceptible to error. For example,an optical path can be made to an unintended port or to an unintendednode. Or, incorrect data may be entered into the path router 140. Theproblem is exacerbated by the fact that networks are becomingincreasingly large and complex.

[0010] Moreover, when new nodes are installed, connections are modified,or when error in connection information is suspected, the entire networkmust be manually analyzed, and the topology manually reconfigured. Nodynamic or automated procedure exists to determine the network topology.

[0011] Accordingly, there remains a need for an improved technique todetermine the connections and topology of an optical network.

SUMMARY

[0012] These needs are met by the present invention.

[0013] According to one aspect of the present invention, an apparatushas an optical switch for routing optical signals, the optical switchincluding ports. The apparatus also includes a light source, a lightdetector, and a control circuit connected to the optical.

[0014] According to a second aspect of the invention, an optical networkincluding a plurality of optical nodes is disclosed. A node includes anoptical switch for routing optical signals, the optical switch includingports. Further, the node has a light source, a light detector, andcontrol circuit connected to the optical switch.

[0015] According to a third aspect of the invention, a method ofdetermining topology of a network is disclosed. First, connectioninformation of a first port of a first node is determined. Then, a pathrouter is updated with the connection information.

[0016] According to a fourth aspect of the invention, a method ofdiscovering an optical interconnect path is disclosed. First, a firstidentification is sent from a first port of a first node. Then, thefirst identification is received at a first port of a second node. Theinterconnect path is the between the first port of the first node andthe first port of the second node.

[0017] Other aspects and advantages of the present invention will becomeapparent from the following detailed description, taken in combinationwith the accompanying drawings, illustrating by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a simplified illustration of an optical networkincluding prior art optical nodes; and

[0019]FIG. 2 is a simplified illustration of an optical networkaccording to one embodiment of the present invention.

DETAILED DESCRIPTION

[0020] As shown in the drawings for purposes of illustration, thepresent invention is embodied in an optical node apparatus having anoptical switch for routing optical signals, the optical switch includingports. The apparatus also includes a light source, a light detector, anda control circuit connected to the optical switch. The optical nodesends its node identification via each of its ports, and also listens toeach of its ports to detect node id's from other optical nodes connectedto the optical node.

[0021] Referring to FIG. 2, an optical network 200 includes a pluralityof optical nodes. For brevity, only three nodes are shown in FIG. 2.They are, node ND 210, node NE 220, and node NF 230. The network 200includes a plurality of input lines represented by lines 202 a, 202 b,and ellipsis 202 c (collectively, “202”) and a plurality of output linesrepresented by lines 204 a, 204 b, and ellipsis 204 c (collectively,“204”). Although only three nodes are shown, the switching network 200may include hundreds or even thousands of interconnected optical nodes.

[0022] Node ND 210 has an optical switch 212, a control circuit 214, anda plurality of input lines and output lines, or ports, designated, forconvenience, ND0 to NDn where n is an integer. Typical values for n maybe 15, 63, or 255. For brevity, the ports of node ND 210 are referredto, collectively, as ports 211. For the illustrated embodiment, theports 211 are ports of node ND 210 as well as ports of the switch 212.The switch 212 may utilize micro mirrors, liquid, or gaseous elements(collectively, “switching element”) to direct or reflect optical signalsfrom a first port to a second port.

[0023] A light source 216 is connected to one of the ports 211 of theswitch 212. The light source 216 may be modulated to produce a lightsignal, which may be routed to any of the ports of the switch 212. Alight detector 218 is connected to another port of the switch 212. Thelight detector 218 may be connected to any of the ports 211 of theswitch 212 to detect light signal on the connected port. In the currenttechnology, light sources may be implemented using or laser diodes. Thelight detectors may be implemented as photodiodes or phototransistorsfor example.

[0024] Semiconductor light sources and detectors are well known in theindustry and can be easily obtained from various manufacturers, forexample, Agilent Technologies, Inc.

[0025] The control circuit 214, connected to the switch 212, controlsthe state of the switching elements to implement routing of the opticalsignals from a first port to a second port. For instance, the controlcircuit 214 may cause the switch 212 to connect port ND1 to port ND9 toroute an incoming optical signal from line 202 b, connected to port ND1,to be routed to port ND9 for forwarding to port NE1 of node NE 220.

[0026] The control circuit 214 may include a node id (for example, “ND”)for node ND 210. Preferably, the node id uniquely identifies node ND 210within the network 200. The control circuit 214 is also connected to thelight source 216 and the light detector 218. Alternatively, the node idmay be supplied by the path router as needed. The node id may furtherinclude a port identification portion that identifies the port (of thenode) through which the communication is taking place.

[0027] Node NE 220 is similarly configured to node ND 210 and has switch222, ports NEO through NEN (collectively, ports 221), light source 226,light detector 228, and control circuit 224. The control circuit 224 isconnected to the switch 222, the light source 226, and the lightdetector 228, and has a node id (for example, “NE”) for node NE 220.

[0028] The technique of determining the topology, or the connectioninformation, of network 200 can be explained using nodes NE 220 and ND210. Control circuit 224 causes light detector 226 to produce opticalsignals (“identification signal”) identifying node NE 220 such as signalcorresponding to node id “NE”. The identification signal may be sent toeach of the ports 221 by routing, using switch 222, the identificationsignal to each of the ports 221. Preferably, the identification signalalso includes information regarding which port of node NE 220 theidentification signal is being sent from.

[0029] The identification signal is received by node ND 210. Controlcircuit 214 of node ND 210 causes light detector 218 to receive opticalsignals from each of ports 211 of node ND 210. When light detector 218is connected to port ND9, light detector 218 receives the identificationsignal from port NE1 of node NE 220. The received identification signalis forwarded to control circuit 214. With the received identificationsignal, control circuit 214 recognizes that its port ND9 is connected toport NE1 of node NE 220 and stores this connection information, forwardsthe connection information to a path router 240 to update the pathrouter 240, or both. The connection is illustrated by connection 250 inFIG. 2. Additionally, control circuit 214 may send the connectioninformation to another node, not shown, such that the other node isinformed about the connection 219.

[0030] Based on the available paths, the path router 240 can then makeoptical path connections as requested.

[0031] The path router 240 may include the following components: (1)information on the physical path topology; (2) Switch configuration(number of ports, etc.); and (3) current list of requested optical pathconnections including dynamic requests to change optical paths. Theserequests need not know the physical topology of the network but ratherspecification of the endpoint to endpoint connection. The path router240 maps the optical path connection requests to physical switch changesbased upon the physical topology. The word “connection” includes,without limitation, relatively static port to port switch connections aswell as the physical network topology, or how the switches arephysically connected.

[0032] The process also works in reverse. That is, node ND 210 sends itsnode identification “ND” via its ports 211 as identification signal.When the identification signal is sent on port ND9, node NE 220 detectsthe identification signal, recognizes that its port NE1 is connected toport ND9 of node ND 210, and stores this connection information. Theconnection information is then reported to the path router 240.

[0033] Therefore, under the present invention, the topology of thenetwork is dynamically determined using self-identifying nodes such asnode ND 210 and node NE 220. In one embodiment of the present invention,all nodes of the network 200 are similarly configured to illustratednodes ND 210 or NE 220. However, this is not required. In the network200, node NF 230 does not include a light source or a light detector;however, its route topology may be manually entered into the pathrouter. In the case that such node is connected to nodes with nodeidentification capability, such topology may be found.

[0034] The connection information detection may be performed for unusedports. That is, for the ports for which no connection informationexists. Alternatively, the connection information detection may beperformed even for used ports using supervisory channels or bands.

[0035] The path router 240 may maintain the connection information in arouting table. Alternatively, the connection information may bemaintained in a distributed manner by the nodes themselves.

[0036] From the foregoing, it will be appreciated that the presentinvention is novel and offers advantages over the current art. Thepresent invention results in an automatic determination of connectioninformation in an optical network, the connection information being lesssusceptible to errors. Although a specific embodiment of the inventionis described and illustrated above, the invention is not to be limitedto the specific forms or arrangements of parts so described andillustrated. For example, each optical node such as node ND 210 mayinclude a plurality of light sources, a plurality of light detectors, orboth. Alternatively, light source 216 may be built outside the node 210with the identification signals being sent to the node via one of theports. Likewise, light detector 218 may be located outside the node 210with the light signals being sent out to the external light detector forprocessing. The invention is limited only by the claims that follow.

What is claimed is:
 1. An apparatus defining a node, the apparatuscomprising: an optical switch for routing optical signals, the opticalswitch including ports; a light source; a light detector; and controlcircuit connected to the optical switch.
 2. The apparatus recited inclaim 1 wherein the control circuit comprises node identification. 3.The apparatus recited in claim 2 wherein the control circuit causes thelight source to send the node identification via a port of the opticalswitch.
 4. The apparatus recited in claim 2 wherein each port of thenode is identified with a port identification.
 5. The apparatus recitedin claim 1 wherein the light source is connected to a first port of theoptical switch for sending optical signal to identify the optical node.6. The apparatus recited in claim 2 wherein the light detector isconnected to a second port of the optical switch for detecting opticalsignals identifying another optical node.
 7. The apparatus recited inclaim 1 wherein the control circuit determines connection information ofa second port of the optical switch by detecting node identificationfrom another apparatus.
 8. The apparatus recited in claim 6 wherein thecontrol circuit updates a path router with the connection information.9. The apparatus recited in claim 1 wherein the control circuit isconnected to a path router that provides the node with nodeidentification.
 10. An optical network comprising: a plurality ofoptical nodes, each node having ports, a first node comprising anoptical switch for routing optical signals, the optical switch includingports; a light source; a light detector; control circuit connected tothe optical switch; and the optical nodes interconnected via the ports.11. The network recited in claim 10 wherein the control circuitcomprises a first node identification.
 12. The network recited in claim10 wherein the light source of the first optical node is connected to afirst port of the optical switch for sending identification signal toidentify the first optical node.
 13. The network recited in claim 12wherein the light detector is connected to a second port of the opticalswitch for detecting optical signals identifying another optical node.14. The network recited in claim 12 wherein the control circuit causesthe light source to send the first node identification via a port of theoptical switch.
 15. The network recited in claim 12 wherein the controlcircuit determines connection information of a second port of theoptical switch by detecting, via the light detector, a second nodeidentification from a second optical node.
 16. The network recited inclaim 15 wherein the control circuit updates a path router with theconnection information.
 17. The network recited in claim 11 furthercomprising a path router having a table of connections, the tableincluding connection information.
 18. The network recited in claim 11further comprising a path router wherein the path router polls the firstnode for connection information.
 19. The network recited in claim 11further comprising a path router having a table of connections definingtopology of the network.
 20. The network recited in claim 19 wherein thefirst node identification is provided by the path router.
 21. A methodof determining topology of a network, the method comprising: determiningconnection information of a first port of a first node; and updating apath router with the connection information.
 22. The method recited inclaim 21 wherein the method of determining connection information of thefirst port of the first node comprises receiving, at the first port ofthe first node, identification signal from a second node.
 23. The methodrecited in claim 21 wherein the first node is identified using a nodeidentification provided by the path router.
 24. A method of discoveringan optical interconnect path, the method comprising: sending, from afirst port of a first node, a first identification of the first node;and receiving, at a first port of a second node, the firstidentification of the first node wherein the interconnect path is thepath between the first port of the first node and the first port of thesecond node.
 25. The method recited in claim 24 further comprising:sending, from the first port of the second node, a second nodeidentification; and receiving, from the first port of the first node,the second node identification of the second node.
 26. The methodrecited in claim 25 further comprising storing, at the second node, theinterconnect path.
 27. The method recited in claim 25 further comprisingreporting the interconnect path to a third node.
 28. The method recitedin claim 25 further comprising reporting the interconnect path to a pathrouter.